A conventional example of a data transfer control technology based on the SAS (Serial Attached SCSI) standard is a technology known as “wide link” in which a plurality of physical links connected in parallel between devices are bundled as a single logical link (referred to hereinbelow as a “logical link”) (see PTL1, for example). A wide link can be formed automatically between an SAS initiator and an SAS expander and between SAS expanders without an instruction being supplied from an SAS initiator.
Furthermore, another SAS-standard data transfer technology is a technology with which a plurality of virtual physical links (also called “logical links” hereinbelow) are formed by subjecting a single physical link to time division (see PTL 1, for example).
These logical links can be set for individual physical links that form a wide link Hence, if a single wide link is formed from two physical links with a maximum data transfer speed (called the “link rate” hereinbelow) of 6 Gbps, four logical links each having a link rate of 3 Gbps can be set in the wide link by setting two logical links with a link rate of 3 Gbps on each individual physical link.
In this case, the SAS initiator is able to establish a connection with a different SAS target via each logical link. Hence, in the above example, the SAS initiator is capable of simultaneously sending and receiving data to and from four SAS targets at the same time.